1. Field
The present invention relates to ties for poured concrete wall forming systems, and more particularly to such ties that provide for retention of reinforcing bars within the forms.
2. State of the Art
Wall forming systems have been in use for many years and in many embodiments. However, most of the systems require a means of support of a pair of spaced apart vertical frames to which a pair of form panels are attached. The frames may be of temporary construction of wood, or even plastic, but are generally of steel and designed for repeated re-use. Whatever the specific construction of the panel framing, cross ties from one to the other are required, to maintain the form frames and panels in true upright position, parallel to each other, and spaced apart the proper distance. The form ties are typically provided in both horizontal and vertical spaced apart relationship, serving to both prevent spreading of the forms and local bowing of the forms under the hydrostatic pressure from the uncured essentially liquid concrete. After cure, frames and panels are removed, leaving the ties within the cured concrete. Protruding ends of the ties are generally removed flush with the concrete, usually by breaking at notches provided for this purpose.
The form ties are also used to support horizontal reinforcing bars during pouring of the concrete. Typically, the reinforcing bars are secured to the form ties by manually twisted wire loops. Overlapping reinforcing bars are similarly secured together. This procedure is always time consuming, and does not promote accuracy in reinforcing bar placement. Fastening of each bar to each tie is generally required, but negligent omissions are common. The bars are often not fastened firmly, are free to slide sidewise along the smooth ties. Because of such shortcomings, several form tie designs have been proposed with specific provisions for securing the reinforcing members. Examples include U.S. Pat. Nos. 3,197,171, 1,784,329 and 3,530,634. The first of these discloses preformed wire clips welded or brazed to a steel form tie to secure the reinforcing bars. The second discloses a reinforcing bar securing clip arrangement punched and sheared from a plate member which is shaped to be used as a form tie. The last discloses a separate, plastic molded spacer and holder for the reinforcing bars. This holder spans across and butts against the opposing form panels. These disclosed solutions to the reinforcing bar placement problem are relatively simple compared to other proposed solutions. U.S. Pat. No. 4,936,540 discloses a form tie in strap form which includes an upwardly opening notch for a single reinforcing member, representing a partial solution to the problem. However it does not address the problem of overlapping reinforcing members, nor of vertical dislodgement of the bars during pouring. All of the devices that are apparently available involve additional expense and provide only partial solutions.
Clearly, an improved form tie construction is needed that is not prohibitively costly and facilitates reliable reinforcing member placement.